Overview
This lecture covers the properties of solutions, focusing on solutes, electrolytes vs. non-electrolytes, and how acids, bases, and water behave in solutions.
Solutes and Solutions
- A solute is a substance that dissolves in a solvent to form a solution.
- Solutes can be molecular (e.g., sugar, hydrogen peroxide, alcohol) or ionic (e.g., sodium chloride, baking soda).
- Dissolution occurs when solute-solvent interactions are stronger than solute-solute interactions.
Electrolytes and Electrical Conductivity
- Electrolytes form conducting solutions when dissolved in water because they produce ions.
- Strong electrolytes dissociate or ionize 100% into ions and use a single reaction arrow.
- Weak electrolytes partially dissociate/ionize; indicated by a double reaction arrow.
- Non-electrolytes dissolve but do not form ions and do not conduct electricity (e.g., sugar, hydrogen peroxide).
Acids and Bases in Solution
- Acids are molecular compounds that ionize in water to form H+ (actually H3O+, hydronium ion).
- Strong acids ionize completely (single arrow); examples: hydrochloric, nitric, sulfuric, perchloric, hydrobromic, and hydroiodic acids.
- Weak acids ionize partially (double arrow); example: acetic acid.
- Bases dissociate to form hydroxide (OH-) ions; strong bases dissociate 100% (hydroxides of Group 1 and Group 2 metals).
- Weak bases (e.g., ammonia) only partially form OH- by reacting with water.
Amphoteric Nature of Water and pH
- Water can act as an acid (donates H+) or a base (accepts H+); this property is called amphoteric.
- Acids have pH < 7, bases have pH > 7, and neutral solutions have pH = 7.
- Universal indicator can be used to detect solution pH.
Key Terms & Definitions
- Solute — substance dissolved in a solvent.
- Electrolyte — substance that produces ions in water, allowing the solution to conduct electricity.
- Non-electrolyte — substance that dissolves in water but does not produce ions.
- Strong electrolyte — completely dissociates or ionizes in water.
- Weak electrolyte — partially dissociates or ionizes in water.
- Ionize — process by which a molecular compound forms ions in solution.
- Dissociate — process by which ionic compounds separate into ions in solution.
- Hydronium ion (H3O+) — the actual form of H+ in aqueous solution.
- Amphoteric — substance that can act as both an acid and a base.
Action Items / Next Steps
- Memorize the list of strong acids and strong bases.
- Review which substances are electrolytes and non-electrolytes based on their behavior in water.
- Watch the suggested video demonstration on conductivity if you haven't already.
- Prepare for lab comparing conductivity of various acids and bases.